Almadén: Remediation techniques in the Almadén: Remediation techniques in the largest mercury mining district of the largest mercury mining district of the
worldworld
Pablo L. HiguerasPablo L. Higueras
E.U.P. Almadén, Univ. of Castilla-La Mancha E.U.P. Almadén, Univ. of Castilla-La Mancha (Spain)(Spain)
CCMS Meeting, Prevention And Remediation Issues In Selected Industrial Sectors Pilot Study. Baia Mare (Romania), Sept. 7-11, 2003
General IndexGeneral Index
► Geology and miningGeology and mining► MetallurgyMetallurgy► Environmental concernsEnvironmental concerns► Hazards/risksHazards/risks► Remediation issuesRemediation issues
Work doneWork done Work to doWork to do
GeologyGeology
► LocationLocation► Regional geologyRegional geology► Types of cinnabar depositsTypes of cinnabar deposits
Geology: LocationGeology: Location
The Almadén syncline
Geology: Regional GeologyGeology: Regional Geology
Geology: Types of Hg Geology: Types of Hg depositsdeposits► Two major types:Two major types:
StrataboundStratabound EpigeneticEpigenetic
► Stratiform mineralizations: Almadén Stratiform mineralizations: Almadén TypeType Disseminated cinnabar (1-7% Hg) in the
“Criadero” Quartzite Zonal relationship with the “frailesca” rock Vary scarce pyrite Very variable dimensions: 7.5 Mfl. in Almadén,
350.000 fl. in El Entredicho
Geology: Types of Hg Geology: Types of Hg depositsdeposits
Flask: commercial unit for mercury trade. 1 fl: 34.5 kg
El Entredicho open pit
5-10% Hg
Geology: Types of Hg Geology: Types of Hg depositsdeposits► Stratabound mineralizations: Almadén Stratabound mineralizations: Almadén
MineMine Active since more than 2.000 yearsActive since more than 2.000 years Non-stop mining activityNon-stop mining activity
Almadén mineAlmadén mine
► Two branches (Two branches (ramasramas):): Rama Sur: the first in activity, closed from 18 Rama Sur: the first in activity, closed from 18
Century to the 80s, active again until May 2002 (final Century to the 80s, active again until May 2002 (final closure)closure)
Rama Norte: discovered in 1700, in activity until Rama Norte: discovered in 1700, in activity until 19921992
Underground mining: Cut Underground mining: Cut & fill& fill
Almadén mineAlmadén mine
► Epigenetic (discordant) Epigenetic (discordant) mineralizations: Las Cuevas typemineralizations: Las Cuevas type Cinnabar in veins and semimassive
replacements Cross-cutting the “frailesca” rock Pyrite much more common than in
stratiform deposits Minor size - Las Cuevas: 150.000 fl.
Geology: Types of Hg Geology: Types of Hg depositsdeposits
Las Cuevas: cinnabar vein filling
Las Cuevas: cinnabar replacement of Frailesca
Up to 30% Hg
Las Cuevas mineLas Cuevas mine
Las Cuevas mineLas Cuevas mineUnderground mining, VCR (Vertical Crater Retreat)
MetallurgyMetallurgy
► Roasting: HgS + hot Roasting: HgS + hot Hg Hg00 + S + S00
► Evolving methods, with reduction of Evolving methods, with reduction of Hg vapor emission:Hg vapor emission: ““Xabecas” furnaces (12 Century - 1646)Xabecas” furnaces (12 Century - 1646) ““Bustamante” furnaces (1646 - 1930)Bustamante” furnaces (1646 - 1930) ““Idrija” and others furnaces (1930-1957)Idrija” and others furnaces (1930-1957) ““Pacific” furnaces, propane fuelled (1954-2005)Pacific” furnaces, propane fuelled (1954-2005)
MetallurgyMetallurgy
► Xabecas furnacesXabecas furnaces► Hand work made by prisonersHand work made by prisoners
MetallurgyMetallurgy
► Aludeles furnacesAludeles furnaces
MetallurgyMetallurgy
► Pacific furnacesPacific furnaces Multilevel systemMultilevel system Propane fueledPropane fueled
Environmental concernsEnvironmental concerns
► Mercury cycleMercury cycle► In airIn air► In soils and mine dumpsIn soils and mine dumps► In water and stream sedimentsIn water and stream sediments► In plantsIn plants► In faunaIn fauna
► Mercury cycleMercury cycle
Environmental concernsEnvironmental concerns
Environmental concernsEnvironmental concerns
► Mercury Mercury in airin air
Punctual data – Hg: 135,000 ng/m3
Environmental concernsEnvironmental concerns
► Mercury in air: Regional pattern, continuous automobile surveyMercury in air: Regional pattern, continuous automobile survey
Environmental concernsEnvironmental concerns
► Mercury Mercury in soilsin soils
Hg (ppm) Site N
Range Mean StDev ALM 18 6-8,889 2,573 2,979 ECH 8 12-132 57.8 33.1 RD 19 10-188 61.2 55.0 FIT 22 6-69 22.0 16.5
Table 1: Mercury concentrations in soils from different sampling sites. ALM: Almadenejos; ECH: Chillón; RD: Rodoviejo; FIT: Phytoremediation site; N: number of data; StDev: Standard deviation.
Higueras et al. (2003) Journal of Geochemical Exploration, 80: 95-104
► Mercury emission from soilsMercury emission from soils
Environmental concernsEnvironmental concerns
Hg: 8.650 ng/m3
Environmental concernsEnvironmental concerns
► Mercury Mercury in mine dumpsin mine dumps
Ore dumpLas Cuevas
CinnabarMetallic HgSchuetteite
Environmental concernsEnvironmental concerns
► Mercury in mine dumpsMercury in mine dumps
Waste dumpEl Entredicho
Schuetteite
Environmental concernsEnvironmental concerns
► Mercury in mine dumpsMercury in mine dumps
Calcines from Roman times
Hg up to 2,260 μg/g
► Mercury emission from mine dumpsMercury emission from mine dumps
Environmental concernsEnvironmental concerns
Hg: 5,000-50,000 ng/m3
► Mercury in Mercury in waters and stream waters and stream sedimentssediments
► Research in course, with John Gray (USGS) Research in course, with John Gray (USGS) and Mark Hines (Univ. Massachusetts Lowell)and Mark Hines (Univ. Massachusetts Lowell)
► Sampling of the main river course Sampling of the main river course (Valdeazogues) and other sites(Valdeazogues) and other sites
Environmental concernsEnvironmental concerns
► Valdeazogues river: 9 samples, from Valdeazogues river: 9 samples, from upstream the mining area to some 20 km upstream the mining area to some 20 km downstreamdownstream
Environmental concernsEnvironmental concerns
HgW: 7.61 ng/LHgSS: 0.362 μg/g
HgW: 190 ng/LHgSS: 8.22
μg/g
► Streams from the mining areas to the Streams from the mining areas to the Valdeazogues river: Azogado streamValdeazogues river: Azogado stream HgHgWW: 12,500 ng/L: 12,500 ng/L
HgHgSSSS: 2,260 : 2,260 μμg/gg/g
Environmental concernsEnvironmental concerns
► El Entredicho open pit lakeEl Entredicho open pit lake
Environmental concernsEnvironmental concerns
HgW: 2,800 ng/LHgSS: 935 μg/g
► Mercury in Mercury in wild plantswild plants: several species are : several species are very well adapted to soils very rich in mercuryvery well adapted to soils very rich in mercury
Environmental concernsEnvironmental concerns
Soil: up to 1% Hg
Marrubium officinalis: up to
16,000 μg/g
Almadenejos metallurgical
precinct
► Mercury in wild plants: several species are Mercury in wild plants: several species are very well adapted to soils very rich in mercuryvery well adapted to soils very rich in mercury
Environmental concernsEnvironmental concerns
Las CuevasOld mineral dump
Soil: up to 2.5% Hg
Dittrichia graveolens: up to
16,500 μg/g
► Mercury in wild plants: hyperacumulatorsMercury in wild plants: hyperacumulators
Environmental concernsEnvironmental concerns
El Entredicho
open pit lake
Typha dominguensis: up to 245.000 μg/g
► Mercury in wild plants: hyperacumulatorsMercury in wild plants: hyperacumulators
Environmental concernsEnvironmental concerns
Puddles in mine dumps
Polypogon maritimus: up to 1,500,000 μg/g
► Mercury in wild plants: eatable – wild Mercury in wild plants: eatable – wild asparragusasparragus
Environmental concernsEnvironmental concerns
Up to 7,000 μg/g
► Mercury in Mercury in faunafauna: no data: no data
Environmental concernsEnvironmental concerns
Domestic pigs in Almadenejos metall. precinct
Fishing in Castilseras reservoir
Hazards / RisksHazards / Risks
► For mine workersFor mine workers► For local inhabitantsFor local inhabitants► For trophic chainFor trophic chain► Methylmercury presenceMethylmercury presence
Hazards / RisksHazards / Risks
► For For mine workersmine workers:: Working schedule: Working schedule:
8 days a month, 6 8 days a month, 6 hours in hours in underground jobsunderground jobs
Health monitoring Health monitoring by the mining by the mining company health company health service: blood and service: blood and urineurine
Hazards / RisksHazards / Risks
► For For local inhabitantslocal inhabitants:: Hg vapor in air over WHO standard (1 Hg vapor in air over WHO standard (1
μμg/mg/m33) in inhabitad areas) in inhabitad areas
Hazards / RisksHazards / Risks
► For local inhabitants:For local inhabitants: Hg vapor concentrations in some Hg vapor concentrations in some
buildingsbuildings
Almadén Schoolof Mines
Hg up to 45,000 ng/m3 in some rooms (old museum)
Hazards / RisksHazards / Risks
► For For trophic chaintrophic chain:: WaterWater Fishing Fishing VegetablesVegetables
Hazards / RisksHazards / Risks
► For trophic chain:For trophic chain: WaterWater: low Hg : low Hg
contents in most contents in most natural watersnatural waters
Very low Hg Very low Hg content in drinking content in drinking waterwater
Hg: 1.78 μg/L
Hazards / RisksHazards / Risks
► Drinking water comes from a Drinking water comes from a reservoir away from the mining areareservoir away from the mining area
Hg: 9.08 μg/L
Hazards / RisksHazards / Risks
► For trophic chain: For trophic chain: FishingFishing Local people uses to fish in the Local people uses to fish in the
Valdeazogues river and reservoirs (sport)Valdeazogues river and reservoirs (sport) Black Bass (Black Bass (Micropterus salmoidesMicropterus salmoides), Carp ), Carp
((Cyprinus carpioCyprinus carpio)) Need to control the Hg and MeHg contentsNeed to control the Hg and MeHg contents
Hazards / RisksHazards / Risks
► For trophic chain: For trophic chain: VegetablesVegetables Cattle and wild fauna: high risk, since some Cattle and wild fauna: high risk, since some
wild plants contain quite high mercury levelswild plants contain quite high mercury levels Humans: low mercury contents in agricultural Humans: low mercury contents in agricultural
plants (see phytoremediation section)plants (see phytoremediation section) Some wild eatable plants with higher mercury Some wild eatable plants with higher mercury
levelslevels
Hazards / RisksHazards / Risks
► Methylmercury contents: data on Methylmercury contents: data on studystudy Natural watersNatural waters Soils and stream sedimentsSoils and stream sediments
► ValdeazoguesValdeazogues► Azogado streamAzogado stream► Entredicho pit lakeEntredicho pit lake
Calcine heapsCalcine heaps Almadenejos furnaces ruinsAlmadenejos furnaces ruins
Remediation issuesRemediation issues
► Work doneWork done Phytorremediation - phytoextractionPhytorremediation - phytoextraction Study of crandallitic immobilizatorStudy of crandallitic immobilizator
► Work to doWork to do
►A collaboration between the E.U.P. A collaboration between the E.U.P. Almadén (UCLM), the mining Almadén (UCLM), the mining company and CIEMATcompany and CIEMAT
►TreesTrees►Agricultural plantsAgricultural plants►Spontaneous vegetationSpontaneous vegetation
PhytoextractionPhytoextraction
►Trees: Trees: EucalyptusEucalyptus
• 5 plots, on soils with Hg contents between tens and hundreds gr Hg/t (ppm)
• 4 years of “activity”
• Resulting on Hg contents in dry matter between 500 and 2.080 ppb
PhytoextractionPhytoextraction
► Agricultural plantsAgricultural plants Wheat (Wheat (Triticum aestivumTriticum aestivum), barley (), barley (Hordeum Hordeum
vulgarevulgare) and lupine () and lupine (Lupinus luteusLupinus luteus)) 15 subplots 10x10 m, 3x plant, 3 fallow land, 3 15 subplots 10x10 m, 3x plant, 3 fallow land, 3
spontaneous vegetation (2 years)spontaneous vegetation (2 years) 1 plot 100x50 m, barley (21 plot 100x50 m, barley (2ndnd year) year) Hg contents in plots: tens of Hg ppmHg contents in plots: tens of Hg ppm Samples of the crops were taken at different Samples of the crops were taken at different
growth stages analyzing the Hg loading in the growth stages analyzing the Hg loading in the aerial part and in the root separatelyaerial part and in the root separately
PhytoextractionPhytoextraction
PhytoextractionPhytoextraction
► Agricultural plants: soils Agricultural plants: soils characterizationcharacterization
- PHYSICAL CHARACTERIZATION- PHYSICAL CHARACTERIZATION
Granulometry Real and apparent density
Texture Moisture
- CHEMICAL CHARACTERIZATION- CHEMICAL CHARACTERIZATION
Total mercury Organic matter
pH (H2O, KCl) Carbonates, sulfates and nitrates
Cation Exchange Capacity Conductivity
- MERCURY CHARACTERIZATION- MERCURY CHARACTERIZATION
Mercury speciation: determination of inorganic mercury and
methylmercury
Sequential extraction: geochemical partitioning of mercury
►Soils characteristicsSoils characteristics
GEOCHEMICAL PARTITIONING OF MERCURY
0%
20%
40%
60%
80%
100%
3-1 3-2 4-1 4-2 1-1 2-2
SAMPLES
Residual
Sulforganic
Humic
Fulvic
Exchangeable
Water soluble
PhytoextractionPhytoextraction
PhytoextractionPhytoextraction
►Soils characteristicsSoils characteristics
MERCURY SPECIATION
- Volatile organomercuric compounds not detected
(detection limit = 1 ng g-1)
- Methyl-mercury content lower than 1% of total Hg in all the analyzed samples
►Agricultural plants: resultsAgricultural plants: results First year (2000-2001):First year (2000-2001):
PhytoextractionPhytoextraction
0
0,4
0,8
1,2
1,6
2
(Hg
shoo
t/Hg
root
) rat
io
Wheat
CROPS
DISTRIBUTION OF MERCURY IN THE PLANT vs CULTURE AGE
3 months
5 months
7 months
Barley Lupine
►Agricultural plants, 2Agricultural plants, 2ndnd year year
PhytoextractionPhytoextraction
►Laboratory experiments:Laboratory experiments:
Study of the mercury availability in Study of the mercury availability in soils by means of monitorized soils by means of monitorized lisimeterslisimeters
Being carried out by CIEMAT in Madrid Being carried out by CIEMAT in Madrid
PhytoextractionPhytoextraction
PhytoextractionPhytoextraction
►Mercury recovery from biomassMercury recovery from biomass
Biomass combustion in a fluidized bed Biomass combustion in a fluidized bed oven oven
Recovery from the effluent gas by Recovery from the effluent gas by means of carbon active filtersmeans of carbon active filters
Pyrometallurgy of the Hg-rich carbon Pyrometallurgy of the Hg-rich carbon activeactive
To be carried out by CIEMAT + Chemical To be carried out by CIEMAT + Chemical Engineering Dept., UCLMEngineering Dept., UCLM
► Wild plants: already seenWild plants: already seen
PhytoextractionPhytoextraction
Crandallitic immobilizatorCrandallitic immobilizator
►Lab synthesis of crandallitic Lab synthesis of crandallitic compoundscompounds
3Al(OH)3Al(OH)33 + 2H + 2H33(PO(PO44) + 1/2SrCO) + 1/2SrCO33 + 1/2CaCO + 1/2CaCO33 →→
→→ CaCa0.50.5SrSr0.50.5AlAl33(OH)(OH)66(HPO(HPO44)(PO)(PO44) + CO) + CO22 + 4H + 4H22OO
► Reaction carried out at 60ºC in 1 dmReaction carried out at 60ºC in 1 dm33 flasks flasks
magnetically stirred at 700 rpm under magnetically stirred at 700 rpm under
environmental pressureenvironmental pressure
► Reaction time: 15 daysReaction time: 15 daysMonteagudo et al. (2003) Journal of Chem. Technol. Biotechnol., 78: 399–405
Crandallitic immobilizatorCrandallitic immobilizator
►Characterization of the Characterization of the productproduct Chemical analysisChemical analysis
Composition (% w/w) Amorphous CrystalComposition (% w/w) Amorphous Crystal
O 36.11 51.37O 36.11 51.37Al 24.10 18.75Al 24.10 18.75Sr 13.06 10.83Sr 13.06 10.83P 21.94 14.35P 21.94 14.35Ca 4.79 4.70Ca 4.79 4.70
Crandallitic immobilizatorCrandallitic immobilizator
►Characterization of the Characterization of the productproduct Chemical analysisChemical analysis Grain sizeGrain size
Crandallitic immobilizatorCrandallitic immobilizator
►Characterization of the Characterization of the productproduct Chemical analysisChemical analysis Grain sizeGrain size Scanning Electron Microscopy (SEM)Scanning Electron Microscopy (SEM)
15 days, 60ºC, Room press. 6 months, 200ºC, 15 bar
Crandallitic immobilizatorCrandallitic immobilizator
► Equilibrium and kinetic studiesEquilibrium and kinetic studies Experimental isotherms for the HgExperimental isotherms for the Hg2+2+/(Ca/(Ca2+2+--
SrSr2+2+) exchange) exchange
Parameters of the Langmuir equation
Ion exchange reaction:
2 Ca0,5Sr0,5Al3(OH)6(HPO4)(PO4) + 2 Hg2+ ↔
↔ 2 HgAl3(OH)6(HPO4)(PO4) + Ca2+ + Sr2+
► Equilibrium and kinetic studiesEquilibrium and kinetic studies Experimental isothermsExperimental isotherms Experimental kinetics: equilibrium in Experimental kinetics: equilibrium in ≈ 30 s≈ 30 s
0
20
40
60
80
100
120
0 20 40 60 80 100
Time [s]
q [m
g/g
]
12 ppm
20 ppm
80 ppm
120 ppm
Crandallitic immobilizatorCrandallitic immobilizator
► Equilibrium and kinetic studiesEquilibrium and kinetic studies Experimental isothermsExperimental isotherms Experimental kinetics: Lagergren plot, first Experimental kinetics: Lagergren plot, first
order reactionorder reaction
0
0,5
1
1,5
2
2,5
0 5 10 15 20
Time [s]
Log
[qe-
q] 12 ppm
20 ppm
80 ppm
120 ppm
Kad = 8,72 10-2 s-1
Crandallitic immobilizatorCrandallitic immobilizator
► Recovery studiesRecovery studies Thermal treatment: 800ºC Thermal treatment: 800ºC → 99,9% recovery→ 99,9% recovery Chemical treatment: ClChemical treatment: Cl-- (10 (10-4-4 to 5 10 to 5 10-2-2 M) to M) to
form soluble HgClform soluble HgCl442-2-
0
20
40
60
80
100
0,5 1,5 2,5 3,5 4,5
pH of HCl solution
Hg2
+ [%
Rec
over
y]
0
20
40
60
80
100
Und
isol
ved
Hg-
Cra
ndal
lite
[%] ,
Hg-crandallite dissolution at optimum pH=2.25
Crandallitic immobilizatorCrandallitic immobilizator
►Phytoextraction:Phytoextraction: Poor results with agricultural plantsPoor results with agricultural plants Some possibilities with wild vegetationSome possibilities with wild vegetation
►Crandallitic immobilizator:Crandallitic immobilizator: Good synthesis conditionsGood synthesis conditions High HgHigh Hg2+2+ exchange capacity from exchange capacity from
mercurial waste waters, similar to that mercurial waste waters, similar to that obtained with commercial exchangers obtained with commercial exchangers such as resinssuch as resins
Work done: ConclusionsWork done: Conclusions
Work to doWork to do
► Relay on National and European Relay on National and European foundingfounding
► Techniques to applyTechniques to apply Immobilizator field applicationImmobilizator field application Phytoremediation using wild vegetationPhytoremediation using wild vegetation Electrodecontamination: Collaboration Electrodecontamination: Collaboration
from the University of Malaga (Spain)from the University of Malaga (Spain) Soil and dumps covering to avoid light Soil and dumps covering to avoid light
enhanced mercury vaporizationenhanced mercury vaporization